Scanning - Bit depth |
Scanned images are made up of pixels which combined form a bit-map.
Each pixel is made up of bits, and the greater the number of bits stored for each pixel the larger the amount of colour or greyscale information is available.
| 1 bit | 0 - off (black) or 1 - on (white) | black and white | B&W drawing |
| 4 bit | own palette (0000 to 1111) | 16 colours or greyscales | Colour drawing |
| 8 bit | own palette | 256 colours or greyscales | B&W photo, colour cartoon |
| 16 bit | own palette | 65,536 colours | |
| 24 bit | R(0-255) x G (0-255) x B (0-255) | 16.8 million colours | colour photo |
| 36 bit | 68.7 billion colours |
Suggested bit depths for different output destinations;
| Device | Line art | Contone | ||
| Mono (B&W) | Colour | Mono (B&W) | Colour | |
| Printer | 1 bit | 4 bit | 8 bit | 8/24bit |
| VDU | 1 bit | 4 bit | 8 bit | 8/24 bit |
| Fax | 1 bit | 1 bit | 8 bit | 8/24 bit |
File sizes are directly related to bit depth settings. GIF files work at a maximum of 8 bits while JPG's use 24 bits. Compression reduces the actual file size considerably.
[Rev 01/06/99] 1/4/99 © 1999 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.
